Add AlphaRne key decoder

See https://www.eevblog.com/forum/testgear/hacking-the-hdo1khdo4k-rigol-12-bit-scope/msg4499302/#msg4499302

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>

kd2.go

@@ -0,0 +1,199 @@
+package main
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"flag"
+	"fmt"
+	"hash/crc32"
+	"io/ioutil"
+	"os/user"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+var dataFile string
+var xxKey string
+
+func initCmdline() {
+	flag.StringVar(&dataFile, "f", "Key.data", "file to decode")
+	flag.StringVar(&xxKey, "key", "", "key data")
+	flag.Parse()
+}
+
+func Expand(path string) string {
+	if len(path) == 0 || path[0] != '~' {
+		return path
+	}
+
+	usr, err := user.Current()
+	if err != nil {
+		return path
+	}
+	return filepath.Join(usr.HomeDir, path[1:])
+}
+
+func HexString(data []byte) string {
+	var buf bytes.Buffer
+	for i := 0; i < len(data)-1; i++ {
+		buf.WriteString(fmt.Sprintf("%02X ", data[i]))
+	}
+	buf.WriteString(fmt.Sprintf("%02X", data[len(data)-1]))
+	return buf.String()
+}
+
+const delta = 0x9E3779B9
+
+func mx(sum uint32, y uint32, z uint32, p uint32, e uint32, k []uint32) uint32 {
+	return ((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[p&3^e] ^ z))
+}
+
+func fixk(k []uint32) []uint32 {
+	if len(k) < 4 {
+		key := make([]uint32, 4)
+		copy(key, k)
+		return key
+	}
+	return k
+}
+
+func XXTeaDecrypt(v []uint32, k []uint32) []uint32 {
+	length := uint32(len(v))
+	n := length - 1
+	k = fixk(k)
+	var y, z, sum, e, p, q uint32
+	y = v[0]
+	q = 6 + 52/length
+	for sum = q * delta; sum != 0; sum -= delta {
+		e = sum >> 2 & 3
+		for p = n; p > 0; p-- {
+			z = v[p-1]
+			v[p] -= mx(sum, y, z, p, e, k)
+			y = v[p]
+		}
+		z = v[n]
+		v[0] -= mx(sum, y, z, p, e, k)
+		y = v[0]
+	}
+	return v
+}
+
+var fileKey = []uint32{0xAB12CD34, 0xAB12CD34, 0xAB12CD34, 0xAB12CD34}
+var defaultKey = []uint32{0x03920001, 0x08410841, 0x18C32104, 0x318639C7}
+
+func decodeXXTEA(data []byte, key []uint32) []byte {
+	N := len(data)
+	u32 := make([]uint32, N>>2)
+	for i, _ := range u32 {
+		u32[i] = binary.LittleEndian.Uint32(data[i*4:])
+	}
+	u32d := XXTeaDecrypt(u32, key)
+	res := make([]uint8, N)
+	for i, v := range u32d {
+		binary.LittleEndian.PutUint32(res[i*4:], v)
+	}
+	return res
+}
+
+func parseKey(k string) ([]uint32, error) {
+	parts := strings.Split(k, ",")
+	if len(parts) == 0 {
+		return nil, errors.New("invalid key data")
+	}
+	res := make([]uint32, len(parts))
+	for i, s := range parts {
+		if strings.HasPrefix(s, "0x") {
+			s = s[2:]
+		}
+		x, err := strconv.ParseUint(s, 16, 64)
+		if nil != err {
+			return nil, err
+		}
+		res[i] = uint32(x)
+	}
+	return res, nil
+}
+
+func DecryptFile(name string, key []uint32) ([]uint8, error) {
+	data, err := ioutil.ReadFile(Expand(name))
+	if nil != err {
+		return nil, err
+	}
+	dd := decodeXXTEA(data, key)
+	if bytes.Index(dd, []uint8{0}) < 0x10 {
+		fmt.Printf("raw data:\n%v\n", HexString(dd))
+	} else {
+		fmt.Printf("string data:%v\n", string(dd))
+	}
+	return dd, nil
+}
+
+func parseVendorData(data []uint8) error {
+	crc1 := binary.LittleEndian.Uint32(data)
+	size := binary.LittleEndian.Uint32(data[4:])
+	crc2 := crc32.ChecksumIEEE(data[8 : 8+size])
+	if crc1 != crc2 {
+		return errors.New("vendor crc mismatch")
+	}
+	fmt.Printf("vendor crc ok %x\n", crc1)
+	ofs := 8
+	for ofs < len(data) {
+		l1 := binary.LittleEndian.Uint32(data[ofs:])
+		ofs += 4
+		id := binary.LittleEndian.Uint32(data[ofs:])
+		ofs += int(l1)
+		l2 := binary.LittleEndian.Uint32(data[ofs:])
+		ofs += 4
+		item := data[ofs : ofs+int(l2)]
+		crc1 = binary.LittleEndian.Uint32(item)
+		size = binary.LittleEndian.Uint32(item[4:])
+		strSize := binary.LittleEndian.Uint32(item[8:])
+		crc2 := crc32.ChecksumIEEE(item[8 : 12+size])
+		if crc1 != crc2 {
+			fmt.Printf("crc mismatch id:%x crc:%x,%x\n", id, crc1, crc2)
+			continue
+		}
+		dd := decodeXXTEA(item[12:], defaultKey)
+		ofs += int(l2)
+		//n := bytes.Index(dd,[]uint8{0})
+		n := int(strSize)
+		name := string(dd[:n])
+		n = (n + 3) & (^0x3)
+		edata := make([]uint32, (int(size)-n)>>2)
+		for i := 0; i < len(edata); i++ {
+			edata[i] = binary.LittleEndian.Uint32(dd[n+4*i:])
+		}
+		fmt.Printf("id:%x | str:%v | data:%x\n", id, name, edata)
+	}
+	return nil
+}
+
+func main() {
+	initCmdline()
+	k, _ := parseKey(xxKey)
+	if nil != k {
+		N := len(k)
+		if N < 4 {
+			for i := N; i < 4; i++ {
+				k = append(k, k[N-1])
+			}
+		}
+	} else {
+		if strings.HasSuffix(dataFile, "vendor.bin") {
+			k = fileKey
+		} else {
+			k = defaultKey
+		}
+	}
+	fmt.Printf("using key %x\n", k)
+	data, err := DecryptFile(dataFile, k)
+	if nil != err {
+		fmt.Printf("error %v\n", err)
+		return
+	}
+	if strings.HasSuffix(dataFile, "vendor.bin") {
+		parseVendorData(data)
+	}
+}